Decreasing numbers of fish caught in global fisheries, overcapacity of fishing fleets, and rising demand for fish heighten the negative impacts of illegal, unreported, and unregulated (IUU) fishing and make it increasingly widespread and profitable for those involved. This practice undermines sustainable fisheries management, particularly on the high seas (international waters beyond the jurisdiction of coastal states) and in coastal waters of developing countries, and has substantial social and economic ramifications. Eighty percent of the world’s marine fish stocks are fully or overexploited. Illegal and unreported fishing alone accounts for catches worth as much as $23.5 billion annually; this represents an estimated 11 to 26 million tons of fish, equivalent to about one-fifth of the global reported catch. Crucially, the more fish stocks are exploited, the more the proportion of illegal catch appears to increase.